1. Field of the Invention
The present invention relates to a temperature adjustment apparatus for a temperature adjustment object, such as a semiconductor wafer.
2. Description of the Related Art
Steps for processing a semiconductor wafer, such as a silicon wafer, include steps where the temperature of the silicon wafer must be controlled to a target temperature and the temperature distribution in the plane of the silicon wafer (or the deposited material on the silicon wafer) must be controlled to a desired temperature distribution. In particular, in recent years there has been a requirement for the temperature distribution in the plane of the silicon wafer to be set accurately to a desired temperature distribution (either to make the temperature distribution uniform in the plane or to vary the temperature distribution in different parts of the plane), with a view to improving the quality of semiconductor devices.
Therefore, in order to improve the accuracy of temperature adjustment described above, technology for dividing a thermoelectric module into a plurality of zones and controlling the temperature independently in each zone has been implemented.
FIG. 1 shows a structure of a conventional temperature adjustment apparatus 100.
As shown in FIG. 1, the temperature adjustment apparatus 100 comprises a stage 20 on which a silicon wafer forming a temperature adjustment object (semiconductor wafer) is placed, a heat exchange plate 30 constituted by a cooling plate, for instance, and a thermoelectric module plate 140 which is sandwiched between the stage 20 and the heat exchange plate 30. The thermoelectric module plate 140 is a plate on which the thermoelectric module 40 is disposed, and the portion which functions as the thermoelectric module 40 in the thermoelectric module plate 140 is indicated by diagonal hatching.
As shown in FIG. 2A, in the thermoelectric module 40, temperature adjustment side electrodes 41 are disposed on the stage 20 side, heat exchange plate side electrodes 42 are disposed on the heat exchange plate 30 side, the temperature adjustment electrodes 41 are connected to one end surface of thermoelectric elements 43P, 43N, and the heat exchange plate side electrodes 42 are connected to the other end surface of the thermoelectric elements 43P, 43N. The thermoelectric module 40 is constituted by electrically connecting P-type thermoelectric elements (thermoelectric semiconductors) 43P and N-type thermoelectric elements (thermoelectric semiconductors) 43N in alternating fashion, by means of the electrodes 41 and 42.
The thermoelectric module 40 is operated by passing an electric current through the heat exchange plate side electrodes 42 via terminals 45. In other words, when the electric current is passed through the P-type and N-type thermoelectric elements 43P and 43N which are connected in series to the temperature adjustment electrodes 41 and the heat exchange plate side electrodes 42, a movement of electric charge occurs between the electrodes and a movement of heat occurs due to the heat (energy) carried by that charge. By this means, the temperature adjustment electrode 41 side, on the one hand, is cooled due to a heat absorbing effect, and the heat exchange plate side electrode 42 side, on the other hand, radiates heat due to a heat generating effect. Furthermore, if the electric current is passed in the opposite direction, then heat is radiated due to a heat generating effect on the temperature adjustment electrode 41 side. In other words, a heat absorbing effect or a heat generating effect is produced in the plane of the stage 20 which corresponds to the temperature adjustment electrode 41 side, depending on the direction in which the electric current is passed. The operation of the thermoelectric module 40 described above is complemented by use of a chiller, to perform temperature adjustment of a silicon wafer on the plane of the stage 20.
FIG. 3 is a plan diagram of a conventional thermoelectric module 40.
The thermoelectric module 40 is arranged so as to be able to control the temperature independently by passing the electric current through the terminals 45 in each of a plurality of zones 11, 12, 13, 14 from the center toward the outside of the stage 20. The central zone 11 is formed in a circular shape, and the respective zones 12, 13, 14 outside this central zone 11 are formed in a ring shape. The terminals 45 of the plurality of zones 11, 12, 13, 14 are disposed inside the zones 11, 12, 13, 14.
As shown in FIG. 1, holes 45a, 30a are formed respectively in the terminals 45 and the heat exchange plate 30, and shafts 51 for passing the electric current are inserted through the holes 45a of the terminals 45 and the heat exchange plate 30. An electric signal line (not illustrated) is electrically connected from the exterior to the shafts 51, and the electric current is passed through the heat exchange plate side electrodes 42.
The patent reference, Japanese Patent Application Publication No. 2000-508119 discloses a composition in which a thermoelectric module is arranged so as to be able to control the temperature independently by passing the electric current via terminals in each of a plurality of zones from the center of the stage toward the outer sides. This reference also describes an invention in which thermoelectric modules are operated independently for each zone, the temperature distribution in the plane of a silicon wafer placed on the stage is made uniform, and the temperature in the plane is controlled in such a manner that the temperature distribution is different in an inner circumferential portion and an outer circumferential portion.
The patent reference, Japanese Patent Application Publication No. 2001-111121 discloses a composition in which an expansion section is provided so as to extend to a position near a bolt installation hole, in a temperature adjustment side electrode on a stage. This bolt installation hole is a hole through which a bolt in inserted to join the stage and the heat exchange plate (water-cooled plate) together.